This section provides background information related to the present disclosure which is not necessarily prior art.
1. Technical Field
The invention relates to a method for separating worn bank notes from a quantity n of bank notes in bank note processing machines.
2. Discussion
Worn bank notes are automatically removed from circulation in bank note processing machines, such as devices for inspecting, counting and packing bank notes, and automated teller machines for the deposit and/or payment of bank notes to bank customers. Wear is present, for example, with soiling or ageing of the bank note. Wear and tear of a bank note further exists if the bank note is grubby, limp or torn, or if the bank note has a large number of folded edges. Bank note processing machines are equipped with sensors to detect the worn bank notes during processing. These sensors measure the value of one or more physical parameters of the bank notes that provide information about the condition of the bank notes. One such physical parameter is optical density, for example. A threshold or threshold value is specified for the measured value of physical size. If this threshold value is reached or exceeded in a bank note, this bank note is separated. If the bank note falls below this threshold value, the bank note remains in circulation. The proportion of bank notes separated from a quantity of bank notes depends on the threshold value and the sensors.
The threshold value can be specified by an operator or manufacturer of a bank note processing machine. Since the proportion of separated bank notes is very sensitive to the level of the threshold value, a threshold value set marginally too high can result in bank notes remaining in circulation that are no longer suitable because of wear. The proportion or rate of separated bank notes is too small in this case. If the threshold value is set too low on the other hand, bank notes are separated that are still suitable for circulation. In this case the proportion or rate of separated bank notes is too high. Since even a minor change in the threshold value sensibly affects the rate of separated bank notes, and the effect of the change can be detected only after a large number of bank notes have been inspected, an adjustment to the threshold value by the manufacturer or operator is made more difficult and leads to poor results.
Determining a threshold value from at least two more bank notes selected by a user at least one of which is clearly used in his opinion and at least one additional one which is clearly suitable for circulation in his view can result in a too large or too small rate of separated bank notes. With this method the rate is decisively dependent on the condition of the selected bank notes.